A method of ultrasonic leaching has been developed for the destructive analysis of magmatic rock samples'. This method was applied to determine three new elements, Ca, Mg and Al, in magmatic rock samples. The accuracy of the ultrasonic leaching method (C-ULM) was tested using standard reference materials (SRMs) and the recovery ratio as K-1 = C-ULM/C-SRM was defined. Another recovery ratio, K-2, was also defined from the results of the conventional dissolution method (CDM), that is K-2 = C-ULM/C-CDM. The accuracy and precision of the method are comparable with those of conventional methods. The following recovery ratios were obtained for Ca, Mg and Al, respectively.